Week 03 · Count With a Box
Monday
A box that counts
// A steps box counts every round
⏱ about 15 min
Welcome back, Code Crew!
Raven finds one more box in the auto-pilot.
Its name tag says steps.
Nova watches the steps box during a test flight.
Each time the ship moves, steps goes up by one.
The steps box is counting!
Rocket wants to learn how a box can count.
WARM-UP: TWO-BOX POWERS
- Read each little program.
- Tap what Nova says.
set height to 3
set speed to height
say speed
?
set height to 6
lower height by 2
say height
?
set height to 5
set speed to height
lower height by 2
say speed
?
A box that counts
The ship moves one step at a time.
After each step, the box adds one.
Three steps, so the box holds 3.
Start at zero
Set steps to 0 starts the count.
Zero means nothing counted yet.
Change steps by 1 counts one more.
set steps to 0 move right change steps by 1 move right change steps by 1 say steps
What do you notice?
Move, count. Move, count.
Only the change lines touch the box.
So Nova says 2.
COUNT THE STEPS
- Count the change lines.
- Tap what Nova says.
set steps to 0
move right
change steps by 1
say steps
?
set steps to 0
change steps by 1
change steps by 1
change steps by 1
say steps
?
set steps to 2
change steps by 1
change steps by 1
say steps
?
Build a one-step counter.
Nova moves one step and says 1.
BUILD A ONE-STEP COUNTER
- Read each card.
- Start at 0 before you count. Say last.
1line 1
2line 2
3line 3
4line 4
Only change lines add to the box.
| after | steps holds | true? |
|---|---|---|
| line 1 | 0 | ? |
| line 2 | 1 | ? |
| line 3 | 1 | ? |
| line 4 | 2 | ? |
| line 5 | 2 | ? |
So many lines!
Counting ten steps takes so many lines.
Is there a faster way?
We find out tomorrow!
Your box can count!
Set steps to 0 starts the count.
Change steps by 1 counts one more.
Great work, Crew!